Most ski boots manufactured for down-hill skiing represent a compromise between being as stif as is desirable for high-performance down-hill skiing and being as comfortable as is desirable for comfort in walking and stride-type skiing. There are some ski boot designs and patents which describe means for adjusting ski boot rigidity, but in each case there is some limitation or disadvantage. It is an object of this invention to make it more practical and convienent for a skier to make a major change in the flexibility of the boot.